Difference in mechanical and energy cost between highly, well, and nontrained runners

INTRODUCTION: Recently it has been shown that endurance training decreases the variability in stride rate. This decrease would lead to a reduction in the mechanical and the energy cost of running. PURPOSE: This study therefore aimed to compare the mechanical and the energy cost of running according to the training status of the runner (highly, well, and nontrained endurance runners). METHODS: The kinetic, potential, and internal mechanical costs (Cke, Cpe, and Cint) were measured with a 3D motion analysis system (ANIMAN3D). The energy cost of running (C) was measured from pulmonary gas exchange using a breath-by-breath portable gas analyser (Cosmed K4b2, Rome, Italy). All the parameters were measured on track, for a speed of 4.84 +/- 0.36 m x s(-1). RESULTS: Highly trained runners did not exhibit significantly lower C compared with well or nontrained runners (4.46 +/- 0.38; 4.33 +/- 0.32; 4.46 +/- 0.46 J x kg(-1) x m(-1), respectively; P = 0.75). However, Cpe was significantly lower in highly and well-trained runners compared with nontrained runners (0.43 +/- 0.07; 0.45 +/- 0.05; 0.54 +/- 0.08 J x kg(-1) x m(-1), respectively; P < 0.05). In contrast, Cint was significantly higher in highly trained runners compared with well and nontrained runners (respectively, 0.80 +/- 0.12; 0.60 +/- 0.09; 0.59 +/- 0.10 J x kg(-1) x m(-1); P < 0.05). CONCLUSION: Although there is a significant difference in Cpe and in Cint between runners of various training status, there is no difference in C. Differences in Cpe and Cint may be associated with the same self-optimizing mechanism that contributes to a reduction in the impact loads during the initial portion of the support phase of the stride.     

The critical power model for intermittent exercise

This paper develops and illustrates the critical power model for intermittent work. Model theoretic development reveals that total endurance time is always a step function of one or more of the four independent variables: work interval power output (P _w), rest interval power output (P _r), work interval duration (t _w), and rest interval duration (t _r). Six endurance-trained male athletes recorded their best performances during the season in 3-, 5-, and 10-km races, and performed three different intermittent running tests to exhaustion in random order, recording their total endurance times. These data were used to illustrate the model and compare anaerobic distance capacities () and critical velocities () estimated from each type of exercise. Good fits of the model to data were obtained in all cases: 0.954<R ²<0.999. Critical velocity was found to be significantly less when estimated using an intermittent versus continuous running protocol.     

Advanced glycoxidation end products in commonly consumed foods

OBJECTIVE: Advanced glycoxidation end products (AGEs), the derivatives of glucose-protein or glucose-lipid interactions, are implicated in the complications of diabetes and aging. The objective of this article was to determine the AGE content of commonly consumed foods and to evaluate the effects of various methods of food preparation on AGE production. DESIGN: Two-hundred fifty foods were tested for their content in a common AGE marker (epsilon)N-carboxymethyllysine (CML), using an enzyme-linked immunosorbent assay based on an anti-CML monoclonal antibody. Lipid and protein AGEs were represented in units of AGEs per gram of food. RESULTS: Foods of the fat group showed the highest amount of AGE content with a mean of 100+/-19 kU/g. High values were also observed for the meat and meat-substitute group, 43+/-7 kU/g. The carbohydrate group contained the lowest values of AGEs, 3.4+/-1.8 kU/g. The amount of AGEs present in all food categories was related to cooking temperature, length of cooking time, and presence of moisture. Broiling (225 degrees C) and frying (177 degrees C) resulted in the highest levels of AGEs, followed by roasting (177 degrees C) and boiling (100 degrees C). CONCLUSIONS: The results indicate that diet can be a significant environmental source of AGEs, which may constitute a chronic risk factor for cardiovascular and kidney damage.     

P-cadherin is up-regulated by the antiestrogen ICI 182,780 and promotes invasion of human breast cancer cells

P-cadherin expression in breast carcinomas has been associated with tumors of high histologic grade and lacking estrogen receptor-alpha, suggesting a link between these proteins. In the MCF-7/AZ breast cancer cell line, blocking estrogen receptor-alpha signaling with the antiestrogen ICI 182,780 induced an increase of P-cadherin, which coincided with induction of in vitro invasion. Retroviral transduction of MCF-7/AZ cells, as well as HEK 293T cells, showed the proinvasive activity of P-cadherin, which requires the juxtamembrane domain of its cytoplasmic tail. This study establishes a direct link between P-cadherin expression and the lack of estrogen receptor-alpha signaling in breast cancer cells and suggests a role for P-cadherin in invasion, through its interaction with proteins bound to the juxtamembrane domain.     

Gamma irradiation induces acetylcholine-evoked, endothelium-independent relaxation and activates K-channels of isolated pulmonary artery of rats

PURPOSE: To test the effects of irradiation (R*) on the pulmonary artery (PA). METHODS AND MATERIALS: Isolated PA rings were submitted to gamma irradiation (cesium, 8 Gy/min(-1)) at doses of 20 Gy-140 Gy. Rings were placed in an organ chamber, contracted with serotonin (10(-4) M 5-hydroxytryptamine [5-HT]), then exposed to acetylcholine (ACh) in incremental concentrations. Smooth muscle cell (SMC) membrane potential was measured with microelectrodes. RESULTS: A high dose of irradiation (60 Gy) increased 5HT contraction by 20%, whereas lower (20 Gy) doses slightly decreased it compared with control. In the absence of the endothelium, 5-HT precontracted rings exposed to 20 Gy irradiation developed a dose-dependent relaxation induced by acetylcholine (EI-ACh) with maximal relaxation of 60 +/- 17% (n = 13). This was totally blocked by L-NAME (10(-4) M), partly by 7-nitro indazole; it was abolished by hypoxia and iberiotoxin, decreased by tetra-ethyl-ammonium, and not affected by free radical scavengers. In irradiated rings, hypoxia induced a slight contraction which was never observed in control rings. No differences in SMC membrane potential were observed between irradiated and nonirradiated PA rings. CONCLUSION: Irradiation mediates endothelium independent relaxation by a mechanism involving the nitric oxide pathway and K-channels.     

Vestibulospinal component of postural control (vestibular function) in very preterm infants (25 to 27 weeks) at 3, 6, and 12 months corrected age

Postural control, which is important for the development of all movement, balance, and locomotion, depends a great deal on the vestibulospinal component of vestibular function in early childhood. Vestibulospinal input is important for muscle power regulation, which, in turn, influences postural control. The aim of this study was to focus particularly on this component of vestibular function during the first year of life in 67 infants with a very short gestational age (25-27 weeks), to search for possible neonatal confounders, and to see whether it influences the course of muscle power development in preterm infants. Outcome was described as being optimal, suspect, or abnormal. The infants were categorized into the Neonatal Medical Index according to the severity of neonatal illness and separately into three groups for neonatal brain ultrasonography findings (normal to severe abnormalities). At the age of 3 months, 20 infants performed optimally on all items testing vestibular function, increasing to 40 at 6 months and 48 at 12 months. This significant improvement (also seen in muscle power regulation) was primarily caused by better head control (during the traction response and prone position), whereas less shoulder retraction and hyperextension were found in the sitting position. Vestibular function was significantly related to brain ultrasonography classification but not to gestational age, birthweight, the Neonatal Medical Index, or gender.     

Assessing chemical exposures during military deployments

Before the first Persian Gulf War, military chemical concerns were focused on life-threatening/performance-impairing effects from exposures to chemical warfare agents. Now, hazards of concern include both high and low levels of chemical warfare agents and toxic industrial chemicals in air, soil, and water. The types of health effects considered have expanded to include both immediate, acute effects (mild and severe), and delayed or chronic outcomes. Because federal exposure standards are not applicable to deployed personnel, the U.S. Army Center for Health Promotion and Preventive Medicine established military-specific exposure guidelines in Technical Guide 230, Chemical Exposure Guidelines for Deployed Military Personnel. Methods used to develop the guidelines address toxicological data limitations, uniqueness of military populations and exposure scenarios, and a risk assessment process compatible with existing military operational risk management doctrine. The Technical Guide 230 helps ensure chemical hazards are addressed in various deployment scenarios.     

In vitro activity of extracts and constituents of Pelagonium against rapidly growing mycobacteria

Extracts of the roots of plants of the Geraniaceae family have been used for many years in South Africa as native herbal remedies and there is circumstantial evidence for efficacy in the treatment of pulmonary tuberculosis. We have examined dried roots of Pelargonium reniforme and P. sidoides for antibacterial activity against rapidly growing mycobacteria. Fractions with activity against Mycobacterium aurum and M. smegmatis were obtained from both plant species by bioassay-guided fractionation of n-hexane extracts and were found to contain mixtures of straight-chain fatty acids. Analysis by gas chromatography–mass spectrometry (GC–MS) of the corresponding fatty acid methyl esters revealed structures with chain lengths ranging from C12 to C26. Unsaturated compounds were analysed as the corresponding dimethyl disulfide adducts to determine double-bond positions. Active mixtures differed in the relative abundance of their components, but all contained 16:0 (palmitic), Δ⁹-18:1 (oleic) and Δ^9,12-18:2 (linoleic acid) as the major components. When tested against M. aurum, M. smegmatis and other rapidly growing mycobacteria (M. fortuitum, M. abscessus and M. phlei), all saturated compounds except 12:0 were devoid of antimycobacterial activity, whereas unsaturated compounds showed antimycobacterial activity related to their degree of unsaturation, their chain length and the bacterial species tested. The most potent compound was linoleic acid, with MIC of 2 mg/l against M. aurum.